1. Field of the Invention
The present invention relates to a process for measuring the mercury concentration within hydrocarbons such as crude oil.
2. Description of Related Art
Hydrocarbons such as crude oil can contain organic mercury, metallic mercury and ionic mercury. Because this mercury can have a deleterious impact on the environment, the catalysts used in the production of all manner of petrochemical products, and the metals used in the construction of associated production equipment, accurately ascertaining the mercury concentration within crude oil is very important. Conventionally, a sample is extracted from the crude oil and heated to generate a gas that contains the mercury, and the level of mercury in the gas is then measured (for example, Japanese Patent application, first Publication No. 2001-221787).
Measurement of the mercury concentration within a hydrocarbon sample using the heating and vaporization method is conducted in the manner described below.
First, in a sample boat containing activated alumina, the hydrocarbon sample is placed and weighed, and additional activated alumina is then placed on top of the sample. Sodium carbonate and calcium hydroxide, which can remove gases interfering with the mercury measurement, are then added. The sample boat is then placed in the combustion furnace of a combustion-type mercury measurement device, and with air flowing through the furnace, the sample is heated, thus generating a gas containing the mercury in vapor form. This gas containing the mercury vapor is then passed through a column packed with gold carrying diatomaceous earth, together with the air flowing through the furnace. As the gas containing the mercury vapor passes through the column, the mercury forms an amalgam with the gold of the gold carrying diatomaceous earth, and is thus trapped by the gold carrying diatomaceous earth. Following trapping of the mercury, the gold carrying diatomaceous earth is heated under a stream of air, generating a gas containing the mercury vapor, and this gas is then fed into a cold atomic absorption detector to measure the quantity of mercury within the gas.
However, when repeated measurements of the mercury concentration are conducted on the same hydrocarbon sample using this method, the value for the mercury concentration changes with each measurement, and the variation in the mercury concentration can be as much as ± several tens percent. Furthermore, when the results are compared with the mercury concentration measured using a different method, which although being both time and labor intensive, is comparatively more accurate, the results from the more convenient method described above are only about ¼ of the value of the more accurate result, meaning the measured mercury concentration values are not particularly reliable.
Patent Reference 1
Japanese Unexamined Patent Application, First Publication No. 2001-221787
(as described in the related art)